Validation/Reconstruction of the Sunspot Number Record, 1841-2007

[ ] L. Svalgaard Easy Tool Kit, Inc., Houston, TX

IUGG July 2007

Sunspot Number (SSN) Applications

- Solar Dynamo- Space Weather/Climate- Cosmic Ray Modulation- Climate Change

Two SSN Series

RINT: 1700 - 2007 (SIDC/ROB)

RG : 1610 - 1995 (Hoyt & Schatten, 1998)

020406080

100120140160180200

1830 1840 1850 1860 1870 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010

Rz

Rg

Sunspot Number Series

1918171615141312111098 20 21 22 23

SSN

Dec

HF

Ellis (1898)

SSN correlated with daily range of geomagnetic elements

SR Ionospheric Current System (Torta et al., 1997)

SR at Hobarton (1848)

Wolf (1875) used the SSN-daily range relationship to adjust the SSN for years before 1848

Rudolf Wolf

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

1740 1750 1760 1770 1780 1790 1800 1810 1820 1830 1840 1850 1860 1870 1880

Evolution of Wolf Sunspot Numbers

W1861 / Rnow

W1875 / Rnow W1880 / Rnow

W1857 / Rnow

Staudacher

2x

25%

y = 0.9301x1.0391

R2 = 0.8932

0

10

20

30

40

50

60

70

0 10 20 30 40 50 60 70

HON

1902-2003rY NGK

rY HON

Step 1

Show that over extended periods of time (decades, centuries) constant, stablerelationships exist between rY at stations such as Niemegk and Honolulu that arewidely separated in longitude and latitude.

0

10

20

30

40

50

60

70

1840 1850 1860 1870 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000

rY (nT)

Median of SR normalized to NGK

Step 2

0

10

20

30

40

50

60

70

1840 1850 1860 1870 1880 1890 1900 1910 1920 1930

Backbone

OSL

rY (nT)

Link together observations of the regular variation observed at long-term stations (normalizing to Niemegk and using Oslo to bridge the gaps for early years) to obtain the variation of SR since 1840

Step 3

Relate average rY to RINT ( & F10.7)

The daily range rY is highly correlated with RINT & F10.7 at all phases of the sunspot cycle

Step 3 (continued)

Use the RINT vs. rY relationship to obtain a new SSN series back to 1840

Step 4

Step 5Cycle Rg Rz

9 1.347 1.02010 1.545 1.31711 1.572 1.19112 1.580 1.37913 1.343 1.40314 1.121 1.15615 1.075 1.18016 1.103 1.23817 1.093 1.16618 1.046 0.99619 0.991 0.90520 0.978 0.97021 0.986 0.98222 0.961 0.94823 1.026 1.036

Correction Factors forreported sunspot numbers.

Obtain correction factors for each cycle for the International and Group SSN series

Provisional SSN Series:Cycles 10 & 11 comparable to 22 & 23

Work in Progress

- Strengthen 1840-present series- Extend before 1840- Determine causes of jumps in 1893 & 1945 - Determine effect of Earth’s decreasing dipole (~10% since 1840)